While the structure of the chromosome is being slowly unravelled, the function of the chromosomal proteins is largely unknown. The focus of our laboratory is the determination of histone function in yeast through genetic and biochemical means. Histone acetylation is a means by which chromosomal folding may be regulated during the cell cycle. Therefore, we propose to analyze this process in detail. We have developed an assay for enzymatic acetylation in yeast and have used this assay to identify a temperature sensitive mutant (MCS-1147) showing decreased acetylase activity at the non-permissive temperature. We propose to a) purify, and characterize the specificity of yeast histone acetylases, b) determine whether enzymes acetylation is cell cycle specific, and c) obtain mutations in other histone acetylase. These experiments would allow us to determine the biological function of acetylation and will be accomplished by classical enzymological techniques as well as in vitro mutagenesis and yeast transformation of yeast histone acetylase genes. The results of these experiments should provide important insight into the in vivo biological function of histone acetylation and have a profound influence on our understanding of the eukaryotic chromosome.